I don’t think there is a complete cure for hyperacusis but a tolerable level of sound or noise can be achieved by gradually exposing the person to sound that is just a tiny bit louder than they feel comfortable with. Over time the sufferer builds up,a tolerance for sounds that today might seem to be above their tolerance level.
On a lighter note, we have a new toilet that is a super flusher but, OMG the noise it makes is enough to wake the dead. I have to keep ear muffs on the toilet tank top and clap them on my ears before flushing. Needless to say, it’s in the ensuite bathroom so it awakens my husband or me depending on which one of us is asleep. Why can’t manufacturers of devices find a way to insulate these things?